Effect of stress history on CPT and DMT results in sand

In order to investigate the effect of stress history on in-situ test results in granular sediments, a series of CPTs and DMTs are performed on Busan sand prepared in the calibration chamber. KD is found to be the most sensitive to the stress history among CPT and DMT measurements. ED and qc are observed to be similarly affected by the stress history and, therefore, the ED–qc relation appears to be almost independent of the stress history. The KD–DR relation established without considering the stress history is likely to overestimate the relative density of OC sand. It is shown that the existence of the pre-stress of the granular sediment can be indirectly recognized by an estimation of the relative density larger than 100% when using the KD–σv′–DR relation suggested for NC sand. Although qc/σv′–KD/K0 and ED/σv′–KD/K0 relations are heavily influenced by the stress history, qc/σm′–KD/K0 and ED/σm′–KD/K0 relations are observed to be independent of the stress history. Based on these relations, charts to evaluate the K0 value from qc and/or DMT indices are developed for both NC and OC sands. The design chart based on ED/σm′–KD/K0 and ED/σv′–KD/K0 relations is expected to be practically useful as the usage of this chart requires only DMT indices. The developed design charts are applicable to Busan sand but different sets of equations and charts may be developed for other sands.

Research Highlights
► KD is considerably more sensitive to the stress history than ED and qc.
► The stress history shows only a slight influence on the qc/(σv′)0.5–DR and ED/(σv′)0.5–DR relations.
► The KD–DR relation is likely to overestimate the relative density of OC sand.
► qc/σv′–KD/K0 and ED/σv′–KD/K0 relations are heavily influenced by the stress history.
► qc/σm′–KD/K0 and ED/σm′–KD/K0 relations are found to be independent of the stress history.
► Design charts based on ED/σm′–KD/K0 and ED/σv′–KD/K0 relations are suggested.